1 //===-- WebAssemblyRegNumbering.cpp - Register Numbering ------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 /// 9 /// \file 10 /// This file implements a pass which assigns WebAssembly register 11 /// numbers for CodeGen virtual registers. 12 /// 13 //===----------------------------------------------------------------------===// 14 15 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h" 16 #include "WebAssembly.h" 17 #include "WebAssemblyMachineFunctionInfo.h" 18 #include "WebAssemblyUtilities.h" 19 #include "llvm/CodeGen/MachineFrameInfo.h" 20 #include "llvm/CodeGen/MachineFunction.h" 21 #include "llvm/CodeGen/MachineRegisterInfo.h" 22 #include "llvm/CodeGen/Passes.h" 23 #include "llvm/Support/Debug.h" 24 #include "llvm/Support/raw_ostream.h" 25 using namespace llvm; 26 27 #define DEBUG_TYPE "wasm-reg-numbering" 28 29 namespace { 30 class WebAssemblyRegNumbering final : public MachineFunctionPass { 31 StringRef getPassName() const override { 32 return "WebAssembly Register Numbering"; 33 } 34 35 void getAnalysisUsage(AnalysisUsage &AU) const override { 36 AU.setPreservesCFG(); 37 MachineFunctionPass::getAnalysisUsage(AU); 38 } 39 40 bool runOnMachineFunction(MachineFunction &MF) override; 41 42 public: 43 static char ID; // Pass identification, replacement for typeid 44 WebAssemblyRegNumbering() : MachineFunctionPass(ID) {} 45 }; 46 } // end anonymous namespace 47 48 char WebAssemblyRegNumbering::ID = 0; 49 INITIALIZE_PASS(WebAssemblyRegNumbering, DEBUG_TYPE, 50 "Assigns WebAssembly register numbers for virtual registers", 51 false, false) 52 53 FunctionPass *llvm::createWebAssemblyRegNumbering() { 54 return new WebAssemblyRegNumbering(); 55 } 56 57 bool WebAssemblyRegNumbering::runOnMachineFunction(MachineFunction &MF) { 58 LLVM_DEBUG(dbgs() << "********** Register Numbering **********\n" 59 "********** Function: " 60 << MF.getName() << '\n'); 61 62 WebAssemblyFunctionInfo &MFI = *MF.getInfo<WebAssemblyFunctionInfo>(); 63 MachineRegisterInfo &MRI = MF.getRegInfo(); 64 65 MFI.initWARegs(MRI); 66 67 // WebAssembly argument registers are in the same index space as local 68 // variables. Assign the numbers for them first. 69 MachineBasicBlock &EntryMBB = MF.front(); 70 for (MachineInstr &MI : EntryMBB) { 71 if (!WebAssembly::isArgument(MI.getOpcode())) 72 break; 73 74 int64_t Imm = MI.getOperand(1).getImm(); 75 LLVM_DEBUG(dbgs() << "Arg VReg " << printReg(MI.getOperand(0).getReg()) 76 << " -> WAReg " << Imm << "\n"); 77 MFI.setWAReg(MI.getOperand(0).getReg(), Imm); 78 } 79 80 // Then assign regular WebAssembly registers for all remaining used 81 // virtual registers. TODO: Consider sorting the registers by frequency of 82 // use, to maximize usage of small immediate fields. 83 unsigned NumVRegs = MF.getRegInfo().getNumVirtRegs(); 84 unsigned NumStackRegs = 0; 85 // Start the numbering for locals after the arg regs 86 unsigned CurReg = MFI.getParams().size(); 87 for (unsigned VRegIdx = 0; VRegIdx < NumVRegs; ++VRegIdx) { 88 Register VReg = Register::index2VirtReg(VRegIdx); 89 // Skip unused registers. 90 if (MRI.use_empty(VReg)) 91 continue; 92 // Handle stackified registers. 93 if (MFI.isVRegStackified(VReg)) { 94 LLVM_DEBUG(dbgs() << "VReg " << printReg(VReg) << " -> WAReg " 95 << (INT32_MIN | NumStackRegs) << "\n"); 96 MFI.setWAReg(VReg, INT32_MIN | NumStackRegs++); 97 continue; 98 } 99 if (MFI.getWAReg(VReg) == WebAssembly::UnusedReg) { 100 LLVM_DEBUG(dbgs() << "VReg " << printReg(VReg) << " -> WAReg " << CurReg 101 << "\n"); 102 MFI.setWAReg(VReg, CurReg++); 103 } 104 } 105 106 return true; 107 } 108